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JSONRPC 2.0 authentication with gamebank authorities

Specification

Design Goals

• Do not require request header modification.
  • Result: Signature/auth must be in message body
• Signed requests do not violate json-rpc spec.
  • Result: Extensions must go into params.
• Method name is not obscured so that it may be routed properly to the correct handler/backend.
  • Result: method remains unchanged by signing.

Signed request

Requests are signed with gamebank keys belonging to the sender.

Example JSON-RPC request:

{
    "jsonrpc": "2.0",
    "id": 123,
    "method": "foo.bar",
    "params": {
        "hello": "there"
    }
}

Above request signed with the posting key belonging to foo:

{
    "jsonrpc": "2.0",
    "method": "foo.bar",
    "id": 123,
    "params": {
        "__signed": {
            "account": "foo",
            "nonce": "1773e363793b44c3",
            "params": "eyJoZWxsbyI6InRoZXJlIn0=",
            "signatures": [
                "1f02df499f15c8757754c11251a6e5238296f56b17f7229202fce6ccd7289e224c49c32eaf77d5905e2b4d8a8a5ddcc215c51ce45c207ef0f038328200578d1bee"
            ],
            "timestamp": "2017-11-26T16:57:40.633Z"
        }
    }
}

Signature creation pseudocode:

# JSON+Base64 request params
params = base64(json_encode(request['params']))

# 8 byte nonce
nonce = random_bytes(8)

# ISO 8601 formatted timestamp
timestamp = date_now() # "2017-11-26T16:57:40.633Z"

# Signer account name
account = 'foo'

# Private posting key belonging to foo
signing_key = PrivateKey('...')

# Signing constant K (sha256('gamebank_jsonrpc_auth'))
K = bytes_from_hex('3b3b081e46ea808d5a96b08c4bc5003f5e15767090f344faab531ec57565136b')

# first round of sha256
first = sha256(timestamp + account + method + params)

# message to be signed
message = sha256(K + first + nonce)


signature = ecdsa_sign(message, signing_key)

Signature validation

1. Entire request must be <64k for sanity/anti-DoS
2. Request must be valid json and json-rpc
3. request['params']['__signed'] must exist
4. request['params']['__signed'] must be the only item in request['params']
5. request['params']['__signed']['params'] must be valid base64
6. request['params']['__signed']['params'] when base64 decoded must be valid json
7. request['params']['__signed']['nonce'] must exist and be a hex string of length 16 (8 bytes decoded)
8. request['params']['__signed']['timestamp'] must exist and be a valid iso8601 datetime ending in Z
9. request['params']['__signed']['timestamp'] must be within the last 60 seconds
10. request['params']['__signed']['account'] must be a valid gamebank blockchain account
11. request['params']['__signed']['signature'] must be a hex string >= 64 chars (32+ bytes decoded)
12. construct first = sha256( request['params']['__signed']['timestamp'] + request['params']['__signed']['account'] + request['method'] + request['params']['__signed']['params'] ).bytes()
13. construct signedstring = sha256( K + first + unhexlify(nonce)).bytes()
14. check signature, signedstring against posting authorities for request['params']['__signed']['account']